The present invention relates to powered systems for adjusting the position of a motor vehicle rearview mirror and particularly relates to such systems where it is desired to automatically move the mirror to a predetermined position in response to a sensed condition. Such automatic mirror adjustment systems are employed to adjust the mirrors outwardly to a predetermined setting for the particular driver identified by an individual code for that driver inputted to the mirror control system through insertion of the key in the ignition switch and also for lowering the mirrors to cover the ground adjacent and behind the vehicle upon the vehicle being placed in reverse gear for backing.
The need for accuracy in positioning the mirror to a predetermined position is paramount in such automatic mirror adjustment systems; and, accordingly there is a need for a sensor to determine the instantaneous position of the mirror and provide an output signal which may be used by the controller to generate a drive signal for the mirror adjustment servo motor.
Heretofore, it has been common practice to use a potentiometer or variable resistor to provide a mirror position feedback signal to the controller in such automatic mirror positioning systems. However, problems have been encountered with the use of potentiometers as a result of variations in ambient temperature affecting the resistance of the element in the potentiometer. Furthermore, in order to achieve the accuracy desired it has been necessary to use precision resistive material in the potentiometer and this has been prohibitively costly for high volume passenger and light truck motor vehicle mirror systems. In addition, the potentiometer has exhibited relatively low reliability because of contact wear.
Thus, it has been desired to provide a way or means of improving the accuracy of a mirror position sensing function in an automatic vehicle rearview mirror positioning system and to provide such a system which is low in manufacturing cost and easy to manufacture and assemble.
The present invention provides an integrally mounted position sensor in a rearview mirror actuator for providing an electrical signal output indicative of the position or movement of the actuator for effecting adjustment of a vehicle rearview mirror. The sensor arrangement of the present invention utilizes a magnetized lead screw for actuating mirror movement with ferromagnetic pole pieces or flux concentrators disposed adjacent the lead screw. A Hall effect sensor, the output of which is proportional to axial movement of the lead screw is disposed between the flux collectors. The sensor arrangement of the present invention is provided in the mirror actuator housing with a minimum of redesign or modification to existing designs.